Interconnect structures of semiconductor devices play a critical role in connecting the various active and functional features of the semiconductor device to one another. Interconnect structures include various openings formed through insulating materials and which expose at least one contact surface. Commonly, a conductive interconnect material is introduced into the opening to contact the exposed contact surface of another conductive interconnect material or an active device feature that is exposed within the opening. It is important to maintain the integrity of the interconnect openings and the surfaces of the respective conductive or active device parts that contact each other through the interconnect openings.
A typical interconnect opening includes a generally vertical opening formed through an insulating layer or layers to expose a subjacent contact surface which may be a conductive wire or active device part. RF or reactive ion etching processes are typically used to form the openings. The etching process used to form the opening through the insulating materials may begin to attack the exposed contact surface as the insulating materials are being removed. To address this problem, an etch-stop layer interposed between the insulating layer and the contact layer has been used. With the presence of the etch-stop layer, the etching process used to etch the interlevel dielectric cannot damage the subjacent contact layer. The etch-stop layer must ultimately be removed, however. A problem faced in today's semiconductor manufacturing industry is that the etch-stop layer is conventionally removed by a plasma ion etching process that may damage the subjacent contact layer due to ion bombardment, the presence of fluorine-containing species or other aggressive etch conditions used to remove the etch-stop layer.
When the underlying contact surface is damaged, the sheet resistance of the contact layers increases and the contact resistance between the underlying conductive material and the conductive material introduced into the opening also increases, degrading the integrity of the electrical contact. Increased contact resistance may cause electrical contact failure and can lead to poor device performance or even complete device failure. It would therefore be desirable to address the shortcomings of conventional interconnect structures and the methods for forming them, by providing a method and structure for forming interconnect structures with undamaged contact surfaces.